Cancers of the bowel, most commonly known as colorectal cancer or colon cancer, are among the most frequent malignancies in economically developed countries (Giovannucci, E.; 1999) and are the third most common cancer in Western countries (Narayan & Roy, 2003). Globally, colorectal cancers cause significant morbidity and mortality, with one million new cases per year, and make up 9% of all cancers diagnosed.
Screening by faecal occult blood tests and flexible sigmoidoscopy is theoretically the most effective means of prevention, however these method are not straightforward for high-risk populations and are not cost-effective.
Although several therapeutic agents approved for the treatment of colorectal cancer are available, they all share the disadvantages of either low response rates and/or unfavourable side-effect profile. Platinum analogues such as carboplatin and oxaliplatin cause problematic side-effects of myelosuppression and peripheral neurotoxicity and also suffer from low response rates. The new drug cetuximab and other monoclonal antibody-based therapies seem to be dependent on the patient's genotype, with large sections of the population having mutations leading to poor response.
There is abundant epidemiological and experimental evidence that regular ingestion of non-steroidal anti-inflammatory drugs (NSAIDs) including acetylsalicylic acid (aspirin) promotes colorectal tumour regression and reduces the relative risk of developing colorectal cancer. There is also substantive evidence that aspirin is specifically cytotoxic against colorectal cancer cells cultured in vitro. However, gastrointestinal toxicity, heartburn and vomiting, renal disturbances and neurological related side-effects preclude the universality of aspirin both as a chemopreventitive agent and as a therapeutic agent.